I'm using OS-X 10.9.5. and tried updating Lightroom from 6.3 to 6.4 using the in-app update function. After the update, Lightroom went into the same spinning-ball-hang with the LR-app using 100% CPU and shown as "not responding" in the activity monitor.I uninstalled LR using the Adobe uninstaller (also had the preferences removed).Repaired disc permissions.Re-installed LR from the original purchased image and then ran the 6.4. patch update.After launch, LR would go into the spinning ball mode again - right after the dialog window appeared informing me about the usage date being submitted to Adobe. I couldn't even click ok in that window.I uninstalled again.Re-installed original version and ran the 6.3. updater.Now LR 6.3. runs fine again.I might mention that I wanted to update because importing videos hangs up my LR, and the release notes of 6.4. said that this update would address such "issues".Bottom line: 6.4 doesn't seem to work on my machine.I'm staying with 6.3. and handle my video elsewhere.I'm not really amused.